Evaluating the Risk of Noise-Induced Hearing Loss Using Different Noise Measurement Criteria

Abstract

Objectives

This article examines whether the Occupational Safety and Health Administration's (OSHA) average noise level (L_AVG) or the National Institute of Occupational Safety and Health's (NIOSH) equivalent continuous average (L_EQ) noise measurement criteria better predict hearing loss.

Methods

A cohort of construction workers was followed for 10 years (2000–2010), during which time their noise exposures and hearing threshold levels (HTLs) were repeatedly assessed. Linear mixed models were constructed with HTLs as the outcome, either the OSHA (L_AVG) or NIOSH (L_EQ) measurement criteria as the measure of exposure, and controlling for age, gender, duration of participation, and baseline HTLs (as both a covariate or an additional repeated measure). Model fit was compared between models for HTLs at 0.5, 1, 2, 3, 4, 6, and 8 kHz using the Akaike information criterion (AIC). The 10th, 50th, and 90th percentiles of hearing outcomes predicted by these models were then compared with the hearing outcomes predicted using the ISO 1999:2013 model.

Results

The mixed models using the L_EQ were found to have smaller AIC values than the corresponding L_AVG models. However, only the 0.5, 3, and 4 kHz models were found to have an AIC difference greater than 2. When comparing the distribution of predicted hearing outcomes between the mixed models and their corresponding ISO outcomes, it was found that L_EQ generally produced the smallest difference in predicted hearing outcomes.

Conclusions

Despite the small difference and high correlation between the L_EQ and L_AVG, the L_EQ was consistently found to better predict hearing levels in this cohort and, based on this finding, is recommended for the assessment of noise exposure in populations with similar exposure characteristics.